The present invention relates to a circuit for reducing the amount of multipath distortion in an FM tuner.
An example of a conventional multipath distortion reducing circuit of this type is shown in FIG. 1. In FIG. 1, the output terminal of a front end 1 is connected to a 10.7 MHz bandpass filter (BPF) 2, the output terminal of which is connected to the input terminal of an FM detector 3. The output terminal of the FM detector 3 is connected to the input terminal of a stereo demodulator 4. The latter provides a left channel output and a right channel output respectively at a left channel output terminal 5 and a right channel output terminal 6. A series circuit of a capacitor C and a switch SW is connected between the output terminals 5 and 6.
When multipath distortion occurs and accordingly the noise level increases to make it difficult to hear the reproduced signal, the switch SW connected between the left channel output terminal 5 and the right channel output terminal 6 is turned on. In this case, high-frequency noise components contained in the right and left channel outputs, which are offensive to the ear and which are opposite in phase to one another, are cancelled out, being shorted by the capacitor C. Thus, the perceived noise level is reduced. However, the circuit is disadvantageous in that, the higher the frequency of the cancelled-out signal components, the larger the ratio of mixing of right and left channels, and the lesser the degree of separation between the two channels.